[8u] RFR: 8210891: Remove unused extutil.h from JDK8u sources

[Dmitry Markov]

Hello,

Could you review the following fix, please?

        bug: https://bugs.openjdk.java.net/browse/JDK-8210891 
<https://bugs.openjdk.java.net/browse/JDK-8210891>
        webrev: http://cr.openjdk.java.net/~dmarkov/8210891/webrev.00/ 
<http://cr.openjdk.java.net/~dmarkov/8210891/webrev.00/>

Removed extutil.h and updated TPRMs accordingly.

Thanks in advance,
Dmitry